Copper foil ferrite phase shifter

ABSTRACT

A microwave phase shifter is comprised of thin aluminum channel base in which are placed a ferrite toroid and dielectric slabs to define a waveguide. A metal foil encloses the assembly, held in place by heat shrinkable tubing.

D United States Patent 11 1 1111 3,758,883

Cox et al. Sept. 11, 1973 [54] COPPER FOIL FERRITE PHASE SHIFTER 3,195,079 7/1965 Burton et al. 333/95 R 3,617,960 ll/l97l L v d ,J. 333/95 R [75] Inventors 'f 3,226,807 H1966 174 010. 8 of Balflmore, 3,576,387 4 1971 Derby 174 010. 3 [73] Assignee: The Bendix Corporation, Baltimore,

Primary Examiner-Paul L. Gensler [22] Fil d; M 15, 1972 Attorney-Bruce L. Lamb. William G. Christoforo 21 Appl. No.: 253,372 et 57 ABSTRACT [52] US. Cl 333/24.l, 29/600, 333/98 R 1 [51] [III-4 Cl. H0lp 1/32 A microwave phase Shifter is comprised of thin alumi [58] Fleld 0 Search 333/24.l, 95 R, 98 R; "um channel base in which are Placed a ferrite toroid 174/DIG' 8; 29/600 and dielectric slabs to define a waveguide. A metal foil encloses the assembly, held in place by heat shrinkable [56] References Cited tubing UNITED STATES PATENTS 3,408,597 10/1968 Heiter .4 333/24.1 3 Claims, 4 Drawing Figures HEAT 34 S H RINKABLE TUBING CONDUCTIVE FOIL 26 FERRlTE 28 TOROID COPPER FOIL FERRITE PHASE SIIIFTER BACKGROUND OF THE INVENTION This invention relates to metallic shell devices and more particularly to microwave waveguides and phase shifters.

Microwave phase shifters normally use as the phase shifter a ferrite toroid, where the word ferrite is used as a general termto cover both ferrite and garnet materials. The toroid is enclosed within a waveguide and is contacted at its top and bottom by the waveguide walls. The contact between the toroid and the waveguide is very critical. Since ferrite materials are magnetostrictive there can be little pressure exerted on the ferrite by the waveguide without loss in phase shift per unit length. In addition, there must be very little air gap along the contact surface. Any voids along this contact surface will cause exitation of unwanted waveguide modes which will result in increased phase shifter insertion loss. As a result, the ferrite fit within the waveguide is usually held to a 0.0005 inch tolerance to insure the required close fit. These limitations on the fit of the toroid within the waveguide necessitate very high precision machining on both the ferrite and the waveguide housing, resulting in high construction cost.

SUMMARY OF THE INVENTION In the embodiment to be described the usual waveguide housing is replaced by a thin aluminum, or other suitable material, channel. A toroid and two dielectric slabs, Rexolite or other suitable material, are placed in the channel. The perimeter of the toroid and the dielectric slabs define the inside surface of a waveguide which is formed by wrapping the assembly with a metal foil. A rubber shim and a lighweight protective spacer may be placed external to the metal foil and the entire device inserted into and held together by a heat shrunk tube. During construction, the heat shrinkable tubing is collapsed around the spacer, metal foil and channel forcing the foil into contact with the toroid and slabs. The rubber shim between the spacer and the metal foil insures foil to toroid contact without excessive localized pressure on the ferrite. The aluminum channel provides mounting surfaces for electrical ports which communicate with the device and adds rigidity to the overall package.

It is thus an object of this invention to provide an inexpensively produced foil clad device.

It is another object of this invention to produce a device of the type described which is useful as a microwave ferrite phase shifter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a phase shifter built in accordance with this invention.

FIG. 2 shows greatly enlarged a transverse section of the device of FIG. 1. FIG. 3 is a perspective view of the invention cut away to better show the details of the internal construction.

. FIG. 4 is a side view of the invention cut away to illustrate the construction of an access port.

DESCRIPTION OF THE PREFERRED EMBODIMENT Refer to the figures wherein like reference numerals refer to like elements, and in particular, refer to FIG. 1. In this figure, a phase shifter built in accordance with the invention is seen. The phase shifter is seen to be comprised of a waveguide shaped body having a generally arcuate cover 18. Cover 18 is preferably light weight but rigid. The phase shifter is enclosed in tubing 16 which has been heat shrunk about the device to hold the parts in intimate contact. A toroid bias wire of the type known to those skilled in the art enters the phase shifter at end 12 and exits at end 14 at access holes 12a and 140, respectively. An end plate 17 is seen within the heat shrunk tubing. Another end plate, identical to the end plate 17 shown, is provided at the other end of the phase shifterbut is not visible in the drawings.

Referring now to FIG. 2 a lightweight channel 22, suitably of aluminum, forms a structural strength'mem ber of the device. Located within the channel and defining the interior of a waveguide are the microwave window slabs 24 and 26, suitably Rexolite. Sandwiched between the Rexolite slabs is a ferrite toroid 28. The Rexolite slabs 24 and 26 are generally of equal thickness so that the toroid is centrally located within the transverse dimension of the waveguide.

As is common in the art, a ceramic filler 30 fills the toroid void. The ceramic is preferably chosen to have the same dielectric constant as the ferrite material. A groove 32 within the ceramic material is provided for the bias wire whose ends are seen in FIG. 1. Of course, at the higher microwave frequencies the void within the toroid will be smaller and the ceramic spacer may not be required. In any event a toroid void filler is an option of the device designer.

An electrically conductive foil, suitably copper, is wrapped about the device, at least to cover the exposed surfaces of the slabs 24 and 26 and the toroid 28. It is desirable at this time to wrap the foil into intimate contact with the aforementioned pieces.

A relatively soft rubber-like shim 20 is sandwiched between the top surface 25 of the subassembly and a cover 18. When the heat shrinkable tubing is shrunk around the final assembly shim 20 will conform to irregularities along its surface and together with cover 18 will gently force the foil into intimate contact with the top surface of toroid 28 and the toroid bottom surface into intimate contact with channel 22. In this manner the toroid is not subjected to undesirable localized high pressure areas. The arcuate top surface of cover 18, while not absolutely necessary to practice the invention, is desirable in that it permits the force exerted by the tubing as shrunk to be more evenly transferred to the shim.

The assembly as to this point described is now slipped into heat shrinkable tubing 16a. The tubing should best extend the entire longitudinal length of the assembly and even overextend both ends so that end plates 17, one of which is seen in FIG. 1 will be held in position after the tubing is shrunk.

Refer now to FIG. 3 where the heat shrinkable tubing is not shown and plate 17 and foil 34 have been cut away to better show the construction of the device. Channel 22 together with slabs 24 and 26, toroid 28 and filler 30 with groove 32 are seen. As shown, to provide a flush end the slabs and toroid stop short of the end of channel 22 to provide just enough space for the thinness of end plate 17. Foil 34, which in FIG. 2 was seen to comprise the inside surface of a resulting waveguide, is here shown folded over the end of the assembly so as to make electrical contact with end plate 17 and the end of channel 22. The hole 12a in spacer 24 is provided for access into groove 32 by the bias wire.

Refer now to FIG. 4 which shows a side view of a phase shifter cut away in the vicinity of an electrical port. The port suitably comprises a coaxial connector 40 while a second part or connector 46 is also provided. The connectors are fastened onto the bottom surface of channel 22, which, it will be remembered is the structural member of the device. The toroid 28 and filler 30 are also seen. A hole 44 is provided through channel 22 and toroid 28 to permit electrical communication between the connector center conductor 42 and the toroid void, which in this embodiment is occupied by filler 30.

In this figure an end plate 17 together with bias wire access holes 12a and 14a are also seen.

Returning now to FIG. 1 it should be plain how the heat shrunk tubing holds the device together and overextending the ends of the device holds the end plates 17 in place.

The method of shrinking heat shrinkable tubing is well known and need not be repeated here. It is suffice to mention that the assembly as shown in FIG. 2 is suitably placed in an oven and baked to shrink the tubing. Of course, the tubing is cut away in the vicinity of ports 40 and 46 to provide access to these ports and to permit the port outer conductor to make good electrical contact with channel 22. Holes 12a and 14a are provided through the tubing for bias wire access.

1. An electrical phase shifter comprising:

spacer meanshaving a cross sectional size approximating the interior dimensions of a waveguide and comprised of a ferrite toroid sandwiched between material which is a relative window to microwave energy; said toroid being centrally located in the sandwich, the perimeter of said spacer means defining the interior surface of said phase shifter, a top and bottom surface of said toroid comprising at least a portion of said interior surface;

electrically conductive material means covering substantially the entire cross-sectional perimeter of said spacer means comprising a structural member which covers approximately one side of said device and a foil sheet which covers substantially the remainder of said cross-sectional perimeter including a first surface of said perimeter which includes said top surface of said toroid;

a rigid plate coextensive with said first surface;

a compressible member coextensive with said rigid plate overlying said first surface exterior of said foiled sheet, said rigid plate overlying said compressible member;

shrinkable tubing enclosing said phase shifter at least to encircle said electrically conductive means,

said rigid plate and said compressible member and shrunk to maintain said electrically conductive means in relatively intimate contact with said spacer means; and, port means for providing electrical communication with the interior portion of said phase shifter.

2. The device of claim 1 wherein said foil sheet comprises copper foil.

3. The device of claim 1 wherein'said shrinkable tubing comprises a heat shrinkable tubing.

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UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,758,883 Dated Segtember 11, 1973 Richard M. Cox, Evan Savatgy Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

At claim 1, hne I4, "device" should be cross-sectional perimeter Signed and sealed this 23rd day of. April 197L (SEAL) Attest:

EDWARD MJ LETCIERJR. C. MAI- SHALL DANN Attesting Officer Commissioner of Patents 

1. An electrical phase shifter comprising: spacer means having a cross sectional size approximating the interior dimensions of a waveguide and comprised of a ferrite toroid sandwiched between material which is a relative window to microwave energy; said toroid being centrally located in the sandwich, the perimeter of said spacer means defining the interior surface of said phase shifter, a top and bottom surface of said toroid comprising at least a portion of said interior surface; electrically conductive material means covering substantially the entire cross-sectional perimeter of said spacer means comprising a structural member which covers approximately one side of said device and a foil sheet which covers substantially the remainder of said cross-sectional perimeter including a first surface of said perimeter which includes said top surface of said toroid; a rigid plate coextensive with said first surface; a compressible member coextensive with said rigid plate overlying said first surface exterior of said foiled sheet, said rigid plate overlying said compressible member; a shrinkable tubing enclosing said phase shifter at least to encircle said electrically conductive means, said rigid plate and said compressible member and shrunk to maintain said electrically conductive means in relatively intimate contact with said spacer means; and, port means for providing electrical communication with the interior portion of said phase shifter.
 2. The device of claim 1 wherein said foil sheet comprises copper foil.
 3. The device of claim 1 wherein said shrinkable tubing comprises a heat shrinkable tubing. 